The present invention relates to a method for determining a length, especially for determining the overlapping length of a wound strip of material, especially of a rubber strip, wherein the strip of material is wound onto a drum. The present invention further relates to a device for performing the inventive method.
During the manufacture of tires, the green tire is produced by winding strips of rubber of different kinds onto a winding drum, whereby the ends commonly overlap. In the context of this invention the term "strip of rubber" is to be understood not only as a strip of material of pure rubber, but also as a strip of material of rubberized fabric, for example, cord fabric. The production of a green tire starts with the application of the liner which is already placed with overlapping ends onto the winding drum. The overlapping length is approximately 30 mm. In the same manner, the carcass layer is subsequently applied, also with overlapping ends. In the course of the further manufacture of the tire, different fabric layers and rubber layers, respectively strips, are applied, also with certain predetermined overlapping lengths.
In the past, the control of the overlapping length has been achieved by having the operating personnel directly measure the overlapping length after the completed application of the strip of material. However, this results in the problem that, since a strip of material which contains unvulcanized rubber is elastically deformable, the visible end of the strip, i.e., the outer layer of the strip of material may be determined, but the beginning of the strip, i.e., the forward end may not be exactly determined because in the area of the beginning, where further layers of material have been applied, a slanted portion results due to elastic deformation within the layers so that the operating personnel no longer know where the exact beginning is located within the area of this slanted portion. This problem is further increased when the strip of material is applied in a plurality of windings.
It is therefore an object of the present invention to provide a method for measuring exactly the overlapping length and to provide a device for performing the inventive method.